In the broad field of light reflectors, it has generally been considered desirable to make such reflectors from metallic substrates. Lightweight metallic materials, such as aluminum, are easily formed to provide the desirable reflector configuations and are easily handled both in manufacturing and installation and do not require elaborate support structures and are not easily susceptible to damage. However, a noticeable problem of such metallic reflectors is that the metal acts not only to reflect visible light, but also to reflect ultraviolet, infrared and other undesirable energy and does not provide a "cool" light which is desirable in many uses of such reflectors.
Accordingly, in order to overcome this deficiency of metallic reflectors, particularly in the field of dental, medical or the like lighting devices, glass substrates have been adopted. As is well known, when properly coated with a dichroic coating, glass reflectors will satisfactorily reflect a substantial portion of visible light and allow infrared and other undesirable energy to pass through the glass reflector so that cool light only is reflected. While the use of a glass substrate with a dichroic coating thereon has overcome the problems set forth above with respect to metallic substrate reflectors and has produced a reflected cool light, other problems have been presented with commercial glass substrate reflectors with dichroic coatings thereon.
In this regard, the assignee of the present invention has heretofore quite successfully commercialized a lighting device for dental and surgical procedures, as disclosed in U.S. Pat. No. 3,191,023, which, although not fully disclosed in such patent, has utilized a reflector having a glass substrate of a predetermined shape set forth in such patent for reflecting light in a predetermined pattern and having a dichroic coating on the rear surface of the glass substrate for reflecting a substantial portion of visible light and for allowing ultraviolet, infrared and other undesirable energy along with some unreflected visible light to pass therethrough, so that cool light only is reflected.
By having the dichroic coating on the rear surface of the reflector, a problem of protection of such dichroic coating was presented inasmuch as the dichroic coating can be easily damaged by cleaning or handling of the reflector. Accordingly, the assignee of the present invention employed a protective TEFLON paint coating over the dichroic coating on the rear surface of the glass substrate of the reflector to aid in preventing damage to the dichroic coating.
This paint coating also advantageously served as a diffuser medium to diffuse light passing through the reflector to reduce undesirable glare from the rear of the reflector. Such glare is quite annoying and disrupting to a dentist, doctor or assistant who is utilizing such lighting device and the diffuser paint coating acts in a similar manner to a lampshade over an ordinary household lamp.
While this reflector was successful in the commercial lighting device of the assignee of the present invention and overcame the above problems, it provided a further problem in that after extended use of the lighting device and the reflector, peeling of the protective diffuser paint coating on the rear surface of the glass substrate occurred which also ultimately resulted in damage to the dichroic coating on such rear surface.
Another approach to prevent such damage to the dichroic coating has been utilized by others in the medical and dental lighting device business by providing what is termed a front surface reflector which utilizes a glass substrate and the dichroic coating on the front surface of the reflector so that such dichroic coating will not be subjected to damage from handling, etc. of the normally exposed rear surface of the glass reflector. The lighting device housing usually surrounds the front surface of the reflector and thereby provides some protection against damage to the dichroic coating.
However, such commercial, front surface reflectors used in medical or dental lighting devices have not heretofore provided any diffusing coating for overcoming the problem of undesirable glare emitting from the rear of the reflector and this has been one of the recognized problems in the industry of such front surface reflectors.